1. Field of the Invention
The present invention relates to a clamping tool used in the cutting of, for example, an electric wire, and particularly, to an improvement in the material of the clamping head of a clamping tool.
2. Description of the Related Art
FIG. 1 shows the construction of a conventional clamping tool 1. As shown in the drawing, the clamping tool 1 comprises a clamping head 2. A substantially elliptical hollow portion 3 is formed by cutting away a front portion of the clamping head 2. A cylinder member, which is mounted to the lower portion of the clamping head 2, comprises a cylinder body 4 fit with the lower portion of the clamping head 2 and a piston rod 5 which makes a reciprocating motion within the cylinder body 4. The piston rod 5 is driven by, for example, a hydraulic system, not shown. A ram member consisting of a ram head 6 and a ram body 7 joined to the ram head 6 in the vertical direction by, for example, a screw is inserted into the cylinder body 4. The ram body 7 is formed of a cylinder having a bottom to which the piston rod 5 is joined. A spring 8 is wound about the piston rod 5 housed within the ram body 7. When the pushing force of the piston rod 5 is released, the spring 8 permits the ram body 7 to be brought back to the original position. A first die member 9.sub.1 is mounted within the hollow portion 3 of the clamping head 2. On the other hand, a second die member 9.sub.2 is mounted to the upper surface of the ram head 5 in a manner to face the first die member 9.sub.1.
The clamping tool of the construction described above is used for cutting, for example, an electric wire stretched between utility poles. In cutting the electric wire, the electric wire is held between the first and second die members 9.sub.1 and 9.sub.2 positioned within the hollow portion 3 of the clamping head 2. Under this condition, the piston rod 5 of the cylinder member is moved upward. Also, the ram head 6 and the ram body 7, which are joined to the piston rod 5, are moved in the same direction. As a result, the second die member 9.sub.2 mounted to the ram head 6 is moved toward the first die member 9.sub.1 so as to compress and cut away the electric wire held between the first and second die members 9.sub.1 and 9.sub.2.
To be more specific, the clamping tool 1 is mounted to the tip of a long hollow rod 11, as shown in FIG. 2. One end of a hose 12, which extends through the hollow rod 11, is joined to the cylinder body 4 of the clamping tool 1, with the other end of the hose 12 being joined to a hydraulic compressor 13. An operator 14 standing on the ground moves the hollow rod 11 so as to allow the clamping tool 1 at the tip of the hollow rod 11 to be engaged with an electric wire 16 held in a high position by a utility pole 15. Under this condition, the compressor 13 is operated so as to enable the clamping tool to perform the functions described previously and, thus, to cut away the electric wire 16.
The clamping tool can also be used for connecting two electric wires held by utility poles. In this case, two electric wires are arranged to contact each other at the free ends and the contact region is covered with a connector. Under this condition, the connector is compressed by operating the clamping tool as described previously so as to achieve a desired connection.
As described above, a heavy load is applied to the clamping head. In the conventional clamping tool described above, the clamping head is formed of a material capable of withstanding repeated use of the clamping tool. For example, the clamping head is formed of a Cr-Mo steel which exhibits a high tensile strength and a high resistance to fatigue. However, the Cr-Mo steel is very heavy, having a specific gravity of 7.8. Since the clamping tool is typically used for cutting an electric wire stretched at a high position or for connecting electric wires held at a high position, it is necessary for the operator operating the clamping tool on the ground to bear a heavy burden. Needless to say, a heavy clamping tool causes the operator to become tired in a short time, leading to a low working efficiency. Also, the clamping tool is often swung, making it difficult to position the clamping tool as desired promptly. This also leads to a low working efficiency. Further, the recent trend toward automation of the cutting or connecting operation raises demands reduction in the weight of the clamping tool.
Under the circumstances, it has been proposed to use a light Ti alloy, e.g., Ti-6Al-4V having a specific gravity of 4.5, for forming the clamping head of the clamping tool. A clamping head formed of the Ti alloy has already been put to practical use in some cases. However, the Ti alloy is not satisfactory in the resistance to fatigue, with the result that the clamping head formed of the Ti alloy tends to be cracked when used repeatedly. In other words, the clamping head formed of the Ti alloy is not satisfactory in reliability. What should also be noted is that the cracked pieces of the clamping head formed of the Ti alloy are scattered at a high speed. As a result, the cracked pieces run a distance of as much as 20 to 30 meters during the cutting or connecting operation of electric wires. Thus, it is unavoidable for the operator to be put under a dangerous condition. Further, the clamping head formed of the Ti alloy noted above is costly, compared with the conventional clamping head formed of a Cr-Mo steel, leading to a high manufacturing cost of the clamping tool.